The present invention relates to a fuel assembly for a boiling water reactor (BWR), and more particularly to a fuel assembly suitable to achieve improved fuel economy with high burn-up when an applicable maximum uranium enrichment is limited, as well as a core employing such a fuel assembly.
Recently, an improvement in fuel economy and a reduction in the amount of radioactive waste (i.e., a reduction in the number of fuel rods removed from the core) have become important issues to be solved in the field of light-water nuclear reactors. For improving fuel economy and reducing the amount of radioactive waste, it is effective to increase discharged exposure (i.e., achieve high burn-up) of a fuel assembly.
For increasing discharged exposure of a fuel assembly, it is required to increase the content of uranium-235 in a uranium pellet for the fresh fuel assembly, namely, raise a mean uranium enrichment (i.e., achieve high enrichment) of the fresh fuel assembly. The following prior arts are known relating to how to raise the uranium enrichment for high burn-up.